This problem assumes that the reader knows how a ko fight works.
This shape looks like the twisted four, but it is at the corner. We note that when the group has only one outside liberty at , Black can turn the status of this group into a ko. This is similar to bent four in the corner.
White cannot escape by , which can be blocked by
.
occupies one of the middle points in the twisted four. When
occupies the other middle point,
takes the ko first.
attempts to set up a oshitsubushi, but this leaves the White group with only one liberty, so
simply captures all the White stones.
If Black wins the ko, he will connect at . The White group becomes a bent three big eye and dies.
If White wins the ko, he will capture at , making two eyes and live.
If connects the 1-1 stone, which is under atari, White dies in gote as a bent three big eye.
If here,
leaves the White group in a bent three.
occupies the other middle point, but
lives.
This lives too.
When White has two outside liberties, he lives without ko.
Even if and
attacks...
sets up a oshitsubushi. The atari at
is too late,
captures two Black stones and makes two eyes.
This discussion is at a slightly higher level than the intended level of the problem.
Whether this is a picnic ko is not clear. If White wins, he lives; if Black wins he dies. Hence, we cannot say that this ko is lopsided. Perhaps White invaded Black's corner and managed to make ko. That kind of thing is not unusual. It is a mistake to think of something as your territory unless your opponent cannot invade to no effect.
Authors
at
What about White trying to escape? If White answers with , Black still needs to play
, so White can connect at
.
Matthias Ernst
at
Brent: No, is an internal ko threat and Black would respond by blocking the connection at
. White would then retake the ko with
, and it would be Black's turn to find a ko threat.
at
Coconuts: Even if black disregards the ko "threat" here and lets white connect, white is not away yet. B at a or b pretty effectively pins the white group down, so unless white has a strong position on the top side of the board, she is still in a lot of trouble.